Sewer Problem - plug letting in water

Hey, here in Mass (Dedham) we had heavy rains and the town's sewer is backed up. I have a plug in the basement that is slowly letting in water. I understand there's nothing I can do now until the waters recede. I had a plumber come over and look: he said that most likely based on some rust in the concrete next to the plug where the water is coming, the hub has cracked and needs to be replaced. I called the town and they say it's my responsibility, while the plumber and the condo-association are telling me it's the town. Any ideas - what can I do (I am handy to a degree but not a professional) and who's responsibility is it after all?